c - 我的代码中存在段错误？

Question

我有以下代码:

main()
{
    struct passenger_node {
        char *name;
        struct passenger_node *next;
    };

    struct flight {
        char airline[MAXNAME];
        int number;
        struct passenger_node *passengers;
    };

    // New passengers are added to the front of the list of passengers.
    void add_passenger(char *name, struct flight *flp) {
          struct passenger_node n;
          n.name = malloc(strlen(name)+1);
          strncpy(n.name, name, strlen(name)+1);
          n.next = flp->passengers;
    };

    void list_passengers(struct flight fl) {
        printf("%s", fl.passengers->name);
    }

    struct flight my_flight;
    strcpy(my_flight.airline, "Air");
    my_flight.number = 111;
    my_flight.passengers = NULL;
    add_passenger("MMM", &my_flight);
    list_passengers(my_flight);
}

我在函数 list_passengers 中的行 fl.passengers->name 出现段错误？谁能告诉我这是为什么？

Answer 1

您的 add_passenger 无法更新 passengers 指针:

void add_passenger(char *name, struct flight *flp) {
      struct passenger_node n;
      n.name = malloc(strlen(name)+1);
      strncpy(n.name, name, strlen(name)+1);
      n.next = flp->passengers;
      flp->passengers = ???;                 //<--- UPDATE HERE
};

您将不得不为此动态分配 passenger_node 并且不能使用本地节点。

void add_passenger(char *name, struct flight *flp) {
      struct passenger_node *np = malloc(sizeof(struct passenger_ndoe));
      if (!np) return;

      np->name = malloc(strlen(name)+1);
      strncpy(np->name, name, strlen(name)+1);
      np->next = flp->passengers;
      flp->passengers = np;
};

您的 list_passengers 也不正确。它只显示第一位乘客，不检查空乘客列表:

void list_passengers(struct flight fl) {
    struct passenger_node *np;

    for ( np = fl.passengers; np != NULL; np = np->next )
        printf("%s\n", np->name);
}